This application claims the priority of Japanese Patent Application No. 2000-266437 filed on Sep. 4, 2000 which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a linear transmission member driving unit for an endoscope, and more particularly to a structure of a driving unit for rotating, by means of a motor, a linear transmission member for changing an observation distance.
2. Description of the Prior Art
In recent years, for the endoscope, there has been proposed an endoscope, to which a mechanism for making an observation distance (or depth of field) variable has been applied (disclosed in, for example, Japanese Patent Laid-Open No. 2000-111806 specification or the like). More specifically, a movable lens for making the observation distance variable is installed in an objective optical system arranged at a tip end portion of the endoscope in such a manner that this movable lens can be driven by means of a linear transmission member consisting of a multiple coiled spring or the like. This linear transmission member is arranged together with a protective tube from the tip end portion to an operating unit of the endoscope, and is coupled to a motor provided within this operating unit. In this respect, the protective tube contains the linear transmission member, whereby it is possible to avoid any interference with other members within the endoscope.
According to such a structure, rotation of the motor is transmitted to a driving unit at the tip end portion by means of the linear transmission member to thereby move the movable lens back and forth through this driving unit, whereby it becomes possible to change the observation distance to be set by the objective optical system. This observation distance is operated by a switch provided in the operating unit or the like so that a focal length can be changed to a far direction or a near direction.
Object of the Invention
In the linear transmission member driving unit for the endoscope, however, the linear transmission member consisting of a multiple coiled spring or the like is contained within the protective tube as described above, and an insertion portion (tip end portion, angle portion and soft portion) of the endoscope is requested to have as fine a diameter as possible, and the protective tube to be arranged within the insertion portion is also formed to be as fine as possible, and therefore, there is a problem that friction between the protective tube and the linear transmission member deteriorates the transmission efficiency of motor rotation.
Also, as the endoscope, various types such as gastroscopes and large intestine scopes have been manufactured, and since each of these endoscopes differs in diameter and length of their insertion portions, the respective protective tubes for them must be also adjusted in diameter and length for each type. On the other hand, on the operating unit side, in which the motor driving unit is arranged, it has been requested to standardize the structure of the driving unit including the protective tube irrespective of the type of the endoscope.
The present invention has been achieved in the light of the above-described problems, and is aimed to provide a linear transmission member driving unit for an endoscope capable of enhancing transmission efficiency of the motor driving force by reducing friction between the linear transmission member and the protective tube as far as possible and making the structure of the driving unit within the operating unit identical even when the endoscope is different in type.
In order to attain the above-described object, there is provided a linear transmission member driving unit for an endoscope according to the present invention, in which the linear transmission member and a protective tube therefor are arranged from a tip end portion to an operating unit, for rotating the linear transmission member by means of a motor to thereby drive an object at the tip end portion, wherein the protective tube is divided into a front-side tube and a rear-side tube having a larger inner diameter than the front-side tube, and the front-side tube and the rear-side tube are connected together within the operating unit.
Also, the linear transmission member can be also divided into a front-side transmission member and a rear-side transmission member having a larger outside diameter than the front-side transmission member.
Another invention is characterized in that a multiple coiled spring formed by winding strands of a predetermined number of threads brought into tight contact in a state, in which space for predetermined intervals is left, is used as the above-described rear-side transmission member.
According to the above-described structure, in the rear-side tube having a larger inner diameter arranged within the operating unit, friction with the linear transmission member is reduced so that the transmission efficiency of the motor can be enhanced. Also, this rear-side tube has an advantage that it can be made to have a constant thickness irrespective of the type of the endoscope.
According to another invention described above, the rear-side transmission member is to be formed by winding strands every four or five pieces while space for, for example, a single thread is left, and this spiral space for a single thread is capable of reducing the friction between the rear-side transmission member and the protective tube.